1. Field
The present disclosure generally relates to the fabrication of composite parts, and deals more particularly with a method and device for compacting composite plies against a tool.
2. Background
Composite parts comprising fiber reinforced polymer resins may be fabricated using any of several techniques. In one technique, a multi-ply, fiber pre-preg charge is laid up and drape formed over a tool, following which the formed charge is compacted and cured. In another technique, a dry fiber pre-form is placed in a mold, vacuum bagged and then infused with resin to produce the desired part shape. The resin infused pre-form is then cured using autoclave or out-of-autoclave processes.
Depending on the fabrication technique used and the geometry of the part, achieving adequate compaction of the formed composite charge may present challenges. For example, bridging of the vacuum bag over some areas of the charge may prevent full compaction pressure from being applied to these areas. Similarly, where the forming tool has features, such as relatively sharp inside corners, it may be difficult to fully form a multi-ply charge into these the corners. When the resin infusion technique is used, compaction pressure applied to the fiber pre-form may be lost as the resin is being introduced. Regardless of the fabrication technique, the application of inadequate compaction pressure may result in the finished part exhibiting resin rich zones that have less than a desired fiber fraction, potentially affecting part performance.
Pressure intensifiers had been developed to intensify the amount of compaction pressure that is applied to local areas of a composite charge, but each has limitations. For example, threaded clamp-type intensifiers lose force as the charge moves (compacts) during the compaction process. Similarly, pressure intensifiers that rely on spring forces move only in two directions as the charge is moves. In some applications, tool or part geometries may prohibit the use of known pressure intensifiers.
Accordingly, there is a need for a device and a method of locally intensifying compaction pressure applied to a formed composite charge. There is also a need for a device and method of the type mentioned above that is simple, easy to use and is adapted to move along with the part charge during compaction in order to maintain a desired, constant compaction pressure.